During electrical testing of a semiconductor device, an electric current may be supplied to relevant components of the semiconductor device under test. With increasing metal layers and flip chip bonding, analysis of the integrated circuits (IC) on the semiconductor device can typically only be done from the backside of the chip through the silicon substrate using infrared imaging. It has been noted that the semiconductor device may heat up during such testing due to power dissipation and may need to be cooled.
In one existing cooling method, a cooled diamond window is used to press on the backside of the semiconductor device. This method allows air-gap lens operation. The diamond window allows the system to perform the analysis through the silicon substrate while testing. The diamond conducts heat from the semiconductor device to an attached copper heat exchanger block. Typically, the heat exchanger uses a cooled liquid or super cooled air. Another version of this method involves having a small opening on the diamond window to allow a Solid Immersion Lens (SIL), which can enhance the imaging resolution, to land on the device.
However, in the above method, the thermal resistance is high between the cold contact (diamond window) and the semiconductor device, and between the cold contact and the heat exchanger block, making it difficult for the user to operate the device at a higher power. In addition, in the above method, device planarity requirements are typically stringent, and passive components protruding from the device may have to be removed.
In another existing cooling method, a liquid jet is used to spray a cooled liquid onto the silicon substrate of the semiconductor device. The sprayed liquid is then collected back to the heat exchanger. However, this method typically can only be used with an SIL which has sealed optics. Also, this method can only cool the device to temperatures above 10 degrees Celsius (° C.).
A need therefore exists to provide an apparatus and method for cooling a semiconductor device that seek to address at least some of the above problems.